842 FERMENTATION 



quite differently from the ordinary yeast globules; they next spread out into strings, 

 with a wall surrounding and connecting the cells ; the original cell-walls then si-< -m t> 

 break, and leave apparently tubular threads branched together. 



The following experiment with malt and some very hard water, shows a perma- 

 nent hardness of 40 and an ordinary hardness of 59, with so little as only (!*) of 

 free ammonia and -003 of albuminoidal ammonia, to the 100,000 grains of watt'-r. I falf- 

 a-pint of this water was placed in a clean glass beaker and covered ; it was crystal 

 bright, and remained so for at least three weeks, depositing only carbonate salts as 

 the water evaporated. Ten corns of malt were then put into the water and the I'r.-ik-er 

 replaced in the window, that it should bo subjected to as much light as possible. The 

 corns eventually sank, and about 48 hours afterwards the water had attained quite a 

 milky turbidity, bubbles of gas were continually being evolved from the corns, and a 

 distinct and very unpleasant odour arose from the fermentation that was evinced, 

 and which most certainly had not any alcoholic odour about it. Upon examination 

 with the microscope, the minute spherical forms in common with yeast were dis- 

 tinctly to be seen, and where there was room for locomotion many of them appeared 

 to bo disporting themselves, very much after the fashion of midges in the air, or tho 

 little water-beetle seen so commonly on the surface of a stream on a summer day ; 

 amongst them there were also the little specks of opaque substance, already noticed 

 in tho microscopical examination of ordinary fermentation with yeast. With only 

 a cursory glance, the observer might easily have been led to suppose that these move- 

 ments were accidental, but after attentive observation it became quite evident that it 

 was organised work with a definite purpose, which appeared to be to form strings of 

 about five globules, not always straight, and, when these strings were completed, they 

 remained at rest. 



Now with these facts before us, let us try to mark out a safe line of conduct for tho 

 guidance of the brewer; and the first step is, undoubtedly, to obtain the alcoholic fer- 

 ment in a state of great purity, and to maintain it in full health and vital energy. 

 Experience proves that these latter qualifications are best secured by allowing tho 

 yeast to have contact only with a cold and still atmosphere ; and the more intense tho 

 cold in contact with it, the more satisfactory will be tho result of its application to 

 the purpose of fermentation, as the most intense cold does not even impair the energy 

 of the ferment. Careful selection and cultivation are the principal means to adopt to 

 preserve or obtain yeast in a state of purity ; and if it be kept from air currents, there 

 is less danger of infection from the mischievous germs that are always present in tho 

 common atmosphere. If grape-juice be introduced into a number of phials, with 

 long, upright, straight necks at the top, thereby giving to the atmosphere free admis- 

 sion to the liquid contained, in process of time spontaneous fermentation generally sots 

 in ; but if the necks be bent short round, and turned downwards, fermentation seldom 

 sets in. This is obviously from the increased difficulty tho circulating atmosphere has 

 in depositing the germs of lacteous ferment upon the fluid. Tho knowledge of these 

 facts is valuable, for it shows to us a simple mechanical arrangement by which we may 

 successfully resist the inoculation of our fresh yeast and sound beer-worts from tho 

 atmosphere. Tho means may be thus described : First, the yeast-safe must be pro- 

 vided with a means of refrigeration, that tho progress of fermentation shall bo com- 

 pletely arrested ; secondly, the circulation of tho atmosphere that has actual contact 

 with tho yeast must be obstructed as much as possible. Antiseptics must not bo 

 resorted to, for whatever will destroy the vitality of either lacteous or butyric ferment, 

 will also have the like effect upon yeast ferment. Neither should it be attempted to 

 decrease acid tendency by the use of neutralising agents, for tho door is thus opened 

 for the advancement of tho acetic change ; and this is why, in the manufacture of lactic 

 acid, that, as tho fermentation advances or proceeds, and lactic acid is produced, it k 

 found necessary to continually make to it additions of carbonate of lime, that tho 

 existing acid may be taken up ; for, if this is not done, tho lactic product ceases to bo 

 formed before the fermentation, is completed. 



By the' aid of scientific investigations prosecuted to the present time, wo are enabled 

 to arrange the different kinds of fermentation and their products. When a glucose 

 solution comes in contact with yeast, about 95 per cent, of it is changed into alcohol 

 and carbonic acid gas, tho remaining portion into glycerine, succinic acid, and other 

 compounds ; if in tho progress of the fermentation, the heat bo allowed to rise consi- 

 derably, some of the alcohol present becomes oxidised, and acetic acid is tho result ; 

 the germs of lactoous ferment also increase rapidly (being already present in tho solu- 

 tion), for it is practically impossible, to prepare a saccharine wort that shall bo entirely 

 free from them ; any breath of air that passes over it, tho vessel that contains it, or any 

 substance whatever that touches tho liquid, may bo tho medium of their introduction 

 and incorporation with it ; and, being there, it is only a question of circumstance and 

 time, when they will assert their presence, lactic acid and maunite being tho products of 



